This invention relates to an annealing method for a compound semiconductor substrate and, more particularly to, an annealing method which is capable of effectively suppressing the slip line generation and offering uniform annealing characteristics for over two-inch diameter compound semiconductor wafers, e.g., GaAs wafers.
In respect to annealing methods for ion-implanted layers of a semiconductor substrate, there are two kinds of annealing methods from the viewpoint of annealing time. One is furnace annealing which uses a conventional electric furnace, and the other is annealing which uses incoherent light such as an infrared lamp, etc. The former method requires several minutes.about.several tens of minutes of annealing time whereas the latter method simply requires several seconds.about.several tens of seconds. In particular, the infrared lamp annealing is more advantageous than the conventional furnace annealing in case a annealing of III-V series compound substrate, e.g., GaAs, InP, etc. That is, in the infrared lamp annealing, re-distribution of the ion implanted impurity is effectively suppressed. Although in the furnace annealing, it is required to use a protection film as an insulation film, e.g., SiO.sub.2, Si.sub.3 N.sub.4, etc., it is not necessary to use such protection film in the infrared lamp annealing method because of the short annealing time.
As explained above, rapid thermal annealing (RTA) using radiation from infrared lamps (e.g. halogen lamps) is a very promising annealing method for compound semiconductor substrates, e.g., ion-implanted GaAs. The great advantages of this method are, as stated above, a short annealing time and its relative simplicity as compared with the conventional furnace annealing. The diffusion of implanted dopants and surface degradation of GaAs wafer due to As dissociation are expected to be suppressed by this short annealing time. In spite of those advantages, only a few papers have been reported so far (Badawl et al. 1984, Cummings et al. 1986) on the application of the RTA method to annealing large-size (2- or 3-inch diameter) GaAs wafers. This is probably because considerable crystallographic slips are induced during RTA. Therefore, in order to apply the RTA method to GaAs IC processing, not only must the aforementioned problem be overcome, but it is necessary to insure that the wafer be uniformly annealed.